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Analysis of lines of mice selected for fat content. 1. Correlated responses in the activities of NADPH-generating enzymes.

Published online by Cambridge University Press:  14 April 2009

Emmanuel A. Asante
Affiliation:
Gene Expression Group, AFRC Institute of Animal Physiology and Genetics Research, Edinburgh Research Station, Roslin, Midlothian EH25 9PS
William G. Hill
Affiliation:
Institute of Animal Genetics, University of Edinburgh, West Mains Road, Edinburgh EH9 3JN
Grahame Bulfield*
Affiliation:
Gene Expression Group, AFRC Institute of Animal Physiology and Genetics Research, Edinburgh Research Station, Roslin, Midlothian EH25 9PS
*
* Corresponding author.
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Estimates of the activities (Vmax) of four enzymes that generate the coenzyme NADPH, an absolute requirement for tissue fatty-acid synthesis, and of the concentration of NADP plus NADPH were made in lines of mice differing in fat content. These lines had been selected from the same base population for 20 generations, and 3 high, 3 low replicates and 1 unselected control were used. Analyses were performed on liver and gonadal fat pad (GFP) of males at 5 and 10 weeks of age. In both the liver and the GFP, measurable activities of the four enzymes: glucose-6-phosphate dehydrogenase (G6PDH), 6-phosphogluconate dehydrogenase (6PGDH), isocitrate dehydrogenase (IDH) and malic enzyme (ME) expressed per mg soluble protein were, with minor exceptions, higher in the Fat (F) than in the Lean (L) lines at both ages; the highest ratio being 2–2 for ME in the GFP. The relationships between these measurable activities (Vmax) and in vivo lipogenesis are not however known. When expressed per gram tissue, the ratios for F to L in the GFP were less than 1 in most cases, presumably because of the very different adipocyte numbers and/or sizes between the lines. There were no significant differences between the lines in the concentration of NADP plus NADPH per gram tissue in liver or GFP, suggesting that F lines converted NADP to NADPH faster than L lines. It is predicted that selection on the enzyme activities would be less efficient than direct selection at changing fat content.

Type
Research Article
Copyright
Copyright © Cambridge University Press 1989

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